1. Field
Embodiments of this invention relate generally to the field of signal processing and more particularly to the field of multi-channel digital audio signal processing.
2. Description of Related Art
Stereophonic (“stereo”) sound systems have two or more separate audio signal channels (e.g., left and right channels). Having at least two audio signal channels allows stereo systems to replicate aural perspective and position of sound sources (e.g., instruments of a stage band). During playback, a listener's proximity to the stereo system's speakers will often determine which instruments or tones they hear. Two-channel stereo systems are often thought to have three distinct places where sound can be perceived. Thus, in addition to left and right channels, a center channel can be formed when an equal and identical sound source comes from both the left and right speakers.
Audiophiles and sound engineers are always searching for increasingly creative methods for processing and manipulating audio channel information. For example, audiophiles and sound engineers have been searching for a technique for cleanly isolating information (e.g., vocals) from a stereo recording's center channel, where the information can be cleanly reintegrated with the original stereo recording. One technique for removing information from the center channel calls for inverting a left or right channel signal and adding the inverted and non-inverted signals together. This operation eliminates information that is common to both channels (i.e., the center channel). Although the technique eliminates center channel information from the original recording, it does not isolate the center channel information for further playback and/or processing. Another limitation of the technique is that the resulting signal is a monophonic signal.